Velocity and anisotropy structure of the uppermost mantle under the eastern Tibetan plateau inferred from Pn tomography

被引:14
作者
Li Yuan [1 ]
Lei Jian-She [1 ]
机构
[1] China Earthquake Adm, Inst Crustal Dynam, Key Lab Crustal Dynam, Beijing 100085, Peoples R China
来源
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION | 2012年 / 55卷 / 11期
关键词
Pn-wave; Uppermost mantle; Velocity heterogeneity; Anisotropy; Eastern Tibetan plateau; CRUSTAL STRUCTURE; CHINA; BENEATH; DEFORMATION; FLOW;
D O I
10.6038/j.issn.0001-5733.2012.11.010
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
In the present study a large number of high-quality Pn arrival times were hand-picked from seismograms recorded by the portable seismic stations, deployed from 2010 to 2011 in the Yunnan region by the Institute of Crustal Dynamics, CEA and recorded by Chinese permanent seismic stations around the eastern Tibetan plateau. Combining with the data from the observational bulletins of Chinese provincial seismic networks, we obtained a new model of seismic velocity and anisotropy of the uppermost mantle under the eastern Tibetan plateau. Our results show obvious lateral heterogeneities in the study region. The old basins and stable blocks, such as the Sichuan and Qaidam basins and Lhasa and Alashan blocks, show prominent high-velocity anomalies, while the Qilian-Qinling fold zone and northern Chuan-Dian diamond-shaped block exhibit relatively weaker high-velocity anomalies. A pronounced north-south trending low-velocity anomaly zone exists from the Songpan-Garze block east of the Longriba fault, southward through the Anning-Zemu fault zone to the southern Chuan-Dian diamond-shaped block. In the Sanjiang fold system, Burma-subduction zone and the region southeast of the Sichuan basin, there are three obvious low-velocity anomalies. Most of crustal major earthquakes occur on the edges of high-velocity anomalies or the transition zone from high to low velocities, suggesting that crustal earthquakes may be somewhat related to the mantle structure. The fast direction of Pn propagation around the eastern Himalayan syntaxis rotates in a clockwise manner, suggesting that it is related to the Indo-Asian collision. The fast direction changes sharply across the Longmenshan fault zone from NE under the Songpan-Garze block in the west to EW under the Sichuan basin in the east, implying that the material flow of the Tibetan plateau is divided into the NE and SW braches when it meets the Sichuan basin. To south of 26 degrees N, in the Chuan-Dian region the Pn fast direction is in an approximate N-S direction, which is consistent with the GPS observations but different from SKS splitting results, suggesting the mechanically coupling of the crust and the uppermost mantle but decoupling at certain depths between the uppermost and lithospheric mantle.
引用
收藏
页码:3615 / 3624
页数:10
相关论文
共 38 条
  • [1] Bassin C., 2000, Eos, V81
  • [2] Global multiresolution models of surface wave propagation: comparing equivalently regularized Born and ray theoretical solutions
    Boschi, Lapo
    [J]. GEOPHYSICAL JOURNAL INTERNATIONAL, 2006, 167 (01) : 238 - 252
  • [3] Study on Pn velocity and anisotropy in the uppermost mantle of the Eastern Himalayan Syntaxis and surrounding regions
    Cui Zhong-Xiong
    Pei Shun-Ping
    [J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2009, 52 (09): : 2245 - 2254
  • [4] Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements
    Gan, Weijun
    Zhang, Peizhen
    Shen, Zheng-Kang
    Niu, Zhijun
    Wang, Min
    Wan, Yongge
    Zhou, Demin
    Cheng, Jia
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2007, 112 (B8)
  • [5] Uppermost mantle velocities beneath China and surrounding regions
    Hearn, TM
    Wang, SY
    Ni, JF
    Xu, ZH
    Yu, YX
    Zhang, XD
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2004, 109 (B11) : 1 - 11
  • [6] Anisotropic Pn tomography in the western United States
    Hearn, TM
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1996, 101 (B4) : 8403 - 8414
  • [7] Uppermost mantle velocities and anisotropy beneath Europe
    Hearn, TM
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1999, 104 (B7) : 15123 - 15139
  • [8] S receiver function analysis of the crustal and lithospheric structures beneath eastern Tibet
    Hu, Jiafu
    Xu, Xingqian
    Yang, Haiyan
    Wen, Limin
    Li, Guangquan
    [J]. EARTH AND PLANETARY SCIENCE LETTERS, 2011, 306 (1-2) : 77 - 85
  • [9] Huang J L, 2003, SCI CHINA SER D, V33, P144
  • [10] Velocity anisotropy in the crust and upper mantle of North China
    Huang Zhong-Xian
    [J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2011, 54 (03): : 681 - 691